Multidirectional fiber-reinforced tape/film articles and the method of making the same

ABSTRACT

High tenacity, high elongation multi-filament polymeric tapes as well as ballistic resistant fabrics, composites and articles made therefrom. The tapes are fabricated from multi-filament fibers/yarns that are twisted together, bonded together, compressed and flattened.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of co-pending application Ser. No.14/503,936, filed on Oct. 1, 2014, which is a Divisional of applicationSer. No. 13/568,097, filed on Aug. 6, 2012, now U.S. Pat. No. 8,852,714,which is a Continuation-in-Part of application Ser. No. 12/539,185,filed on Aug. 11, 2009, now U.S. Pat. No. 8,236,119, the entiredisclosures of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to high tenacity, high elongation multi-filamentpolymeric tapes as well as ballistic resistant fabrics, composites andarticles made therefrom.

DESCRIPTION OF THE RELATED ART

High performance thermoplastic fibers/yarns, such as SPECTRA®polyethylene fibers/yarns or aramid fibers/yarns such as KEVLAR® andTWARON®, are known to be useful for the formation of articles havingexcellent ballistic resistance. Articles such as bullet resistant vests,helmets, vehicle panels and structural members of military equipment aretypically made from fabrics comprising high strength fibers/yarnsbecause of their very high strength to weight performance. For manyapplications, the fibers/yarns may be formed into woven or knittedfabrics. For other applications, the fibers/yarns may be encapsulated orembedded in a polymeric matrix material and formed into non-wovenfabrics. In one common non-woven fabric structure, a plurality ofunidirectionally oriented fibers/yarns are arranged in a generallyco-planar relationship and coated with a matrix material to bind thefibers/yarns together. Typically, multiple plies of suchunidirectionally oriented fibers/yarns are merged into a multi-plycomposite. See, for example, U.S. Pat. Nos. 4,403,012; 4,457,985;4,613,535; 4,623,574; 4,650,710; 4,737,402; 4,748,064; 5,552,208;5,587,230; 6,642,159; 6,841,492; and 6,846,758, all of which areincorporated herein by reference to the extent consistent herewith,which describe ballistic resistant composites including multiple pliesof non-woven fiber/yarn plies.

Composites fabricated from non-woven fabrics are known to stopprojectiles better than woven fabric composites because the componentfibers/yarns in non-woven fabrics are not crimped like the fibers/yarnsin woven materials. Fiber/yarn crimping reduces the ability of thefibers/yarns to stay in tension and immediately absorb the energy of aprojectile, compromising their effectiveness. In addition, projectiledamage to non-woven fabrics is more localized compared to woven fabrics,allowing for enhanced multi-hit performance. However, non-wovencomposite technology remains imperfect. For example, traditionalnon-woven composites are not ideal because a resin coating is generallynecessary to keep the component fibers/yarns bound together. This resinis present in place of a greater quantity of high strength fibers/yarns,and the reduction in overall fiber/yarn content reduces the maximumachievable ballistic resistance efficiency on an equal weight basisrelative to fabrics incorporating no resin coating. In addition,traditional multi-ply non-woven fabrics are formed by cross-plyingadjacent plies at 0°/90° angles, as this construction has been found toachieve greater ballistic penetration resistance than otherconstructions. However, the 0°/90° plies are subject to delaminationwhen the fabric is molded into different contours, such as in thefabrication of helmets and other curved articles. This reduces theirversatility. Accordingly, there is a long felt need in the art fornon-woven composites having improved ballistic performance andversatility.

In this regard, it was recently described in co-pending application Ser.No. 12/539,185, which is incorporated herein by reference, that theballistic-resistance efficiency of a composite may be improved by usingresin coated strips or ribbons as the component elements of a non-wovencomposite rather than resin coated multi-filament yarns. As described inSer. No. 12/539,185, this was first recognized in U.S. Pat. No.4,623,574 which compared the ballistic resistance effectiveness of acomposite comprising ultra-high molecular weight polyethylene (“UHMWPE”) ribbons having a relatively flat, rectangular cross-section (i.e.an aspect ratio of at least about 5) versus a composite formed from UHMWPE multi-filament yarns having a more conventional roundedcross-section. Surprisingly, it was found that the multi-filament yarnhad a higher tenacity than the ribbon, i.e. 30 grams/denier versus 23.6grams/denier, and the Specific Energy Absorption (SEA) value of thecomposite constructed with the ribbon was higher than the SEA of thecomposite constructed with the yarn. Other publications disclosing theformation of articles from flat ribbons or tapes are U.S. Pat. Nos.4,413,110; 4,996,011; 5,002,714; 5,091,133; 5,106,555, 5,200,129;5,578,373; 5,628,946; 6,017,834; 6,328,923; 6,458,727; 6,951,685;7,279,441; 7,470,459; 7,740,779; and 7,976,930, as well as U.S. patentapplication publication 2010/0260968.

These publications teach various methods of forming flat fibrousstructures. In one method, polyethylene filaments are subjected to acontact pressure at an elevated temperature to selectively melt aportion of the filaments and bind them together, followed by compressionof the bound filaments to form a tape. In another method, a polyethylenepowder is compressed at an elevated temperature to bond the powderparticles into a continuous sheet that is further compressed andstretched. Polyethylene tapes so produced are commercially availableunder the trademark TENSYLON®, which is now available from

E. I. du Pont de Nemours and Company of Wilmington, Del., which aredescribed in U.S. Pat. No. 5,091,133. The highest reported ultimatetensile strength (UTS) for such TENSYLON® tapes is 19.5 g/d (1.67 GPa)with an ultimate elongation percentage (UE %) of 1.9%. Polyethylenetapes commercially available from Royal DSM N.V. of The Netherlands asdescribed in their U.S. patent application publication no. 2008/0156345have a reported UTS of 36.7 cn/dtex (41.58 g/denier) and a reported UE %of 3.2%. Polyethylene tapes commercially available from Teijin FibersLtd. of Japan under the trademark ENDUMAX® have a reported UTS rangingfrom 22-28.6 g/denier and a reported UE % ranging from 1.5% to 2%.

While the TENSYLON®, DYNEEMA® and ENDUMAX® polymeric tapes haverepresented advancements in the state of the art, there is a need forpolymeric tapes having improved ultimate elongation at high ultimatetensile strengths (UTS). High UE % is desired because greater UE %translates to greater energy absorption, and greater energy absorptiontranslates to improved ballistic resistance. However, while there areconstant efforts in the art to produce materials having greater UTS,increases in UTS are naturally met with a decrease in UE %. Accordingly,a need for improvements remains ongoing. The present invention providessolutions to this need.

SUMMARY OF THE INVENTION

The invention provides a polymeric tape comprising a flattenedmulti-filament yarn, said yarn comprising a plurality of continuouspolymeric filaments that are twisted together and bonded together;wherein said tape has an ultimate tensile strength of at least 15g/denier and wherein the value of the ultimate tensile strength(g/denier) of the tape multiplied by the ultimate elongation (%) of thetape (UTS*UE) is at least 150.

The invention also provides a polymeric tape comprising a flattenedmulti-filament yarn, said yarn comprising a plurality of continuouspolymeric filaments that are twisted together and bonded together;wherein said tape has an ultimate elongation (y) (%) and an ultimatetensile strength (x) (g/denier) that are proportional to each other andconform to the relationship y=−0.04x+b, where b=5 or greater and x is 15or greater.

The invention further provides a process for forming a layer comprisinga plurality of polymeric tapes, the method comprising:

a) providing a plurality of polymeric tapes, each polymeric tapecomprising a flattened multi-filament yarn, said yarn comprising aplurality of continuous polymeric filaments that are twisted togetherand bonded together with at least about 3 twists per inch of yarn lengthand less than about 15 twists per inch of yarn length, wherein thepolymeric tape has an average cross-sectional aspect ratio of at leastabout 10:1;b) arranging said plurality of polymeric tapes into a side-by-sideplanar array such that only their edges are in contact with each other;c) optionally applying a polymeric binder material onto said array oftapes; andd) applying heat and/or pressure to said array of tapes under conditionssufficient to consolidate said array of tapes into a substantiallyplanar, unitary layer.

Also provided are fabrics, composites and articles formed from suchpolymeric tapes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a first apparatus for producingpolymeric tapes, illustrating a sequence ofcompression-stretching-compression-stretching-compression.

FIG. 2 is a schematic representation of a second apparatus for producingpolymeric tapes, illustrating a sequence ofcompression-compression-stretching.

FIG. 3 is a schematic representation of a third apparatus for producingpolymeric tapes, illustrating a sequence ofstretching-compression-stretching.

FIG. 4 is a schematic representation of a fourth apparatus for producingpolymeric tapes, illustrating a sequence of stretching-three consecutivecompressions-stretching.

FIG. 5 is a schematic representation of a fifth apparatus for producingpolymeric tapes, illustrating a sequence ofstretching-compression-stretching-compression-stretching in a six zoneoven.

FIG. 6 is a schematic representation of a sixth apparatus for producingpolymeric tapes, illustrating a sequence of stretching-two consecutivecompressions-stretching in a four zone oven.

FIG. 7 is a schematic representation of a seventh apparatus forproducing polymeric tapes, illustrating a sequence ofcompression-stretching-stretching at increased tensileforce-compression.

FIG. 8 is a graphic representation illustrating the range of the formulay=−0.04x+b, where b=5 and where b=15.

FIG. 9 is a graphic representation illustrating the UTS*UE % datapresented in Table 1.

In each of FIGS. 1-7 only one yarn end is shown for clarity, but severalyarn ends may be simultaneously treated in parallel by a process of theinvention to produce several polymeric tapes, or a single wide polymerictape.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “tape” refers to a narrow strip of fibrousmaterial having a length greater than its width, wherein a “fibrousmaterial” comprises one or more filaments. The cross-section of apolymeric tape of the invention may be rectangular, oval, polygonal,irregular, or of any shape satisfying the width, thickness and aspectratio requirements outlined herein. Preferably, the tapes are flatstructures having a substantially rectangular cross-section with athickness of about 0.5 mm or less, more preferably about 0.25 mm orless, still more preferably about 0.1 mm or less and still morepreferably about 0.01 mm or less.

In the most preferred embodiments, the polymeric tapes have a thicknessof up to about 3 mils (76.2 μm), more preferably from about 0.35 mil(8.89 μm) to about 3 mils (76.2 μm), and most preferably from about 0.35mil to about 1.5 mils (38.1 μm). Thickness is measured at the thickestregion of the cross-section.

The polymeric tapes of the invention have widths of about 100 cm orless, more preferably about 50 cm or less and still more preferablyabout 25 cm or less. A tape typically has a width less than or equal toabout 6 inches (15.24 cm), with a preferred width of from about 5 mm toabout 50 mm, more preferably from about 5 mm to about 25.4 mm (1 inch),even more preferably from about 5 mm to about 20 mm, and most preferablyfrom about 5 mm to about 10 mm.

These dimensions may vary but the polymeric tapes formed herein are mostpreferably fabricated to have dimensions that achieve an averagecross-sectional aspect ratio, i.e. the ratio of the greatest to thesmallest dimension of cross-sections averaged over the length of thetape article, of greater than about 10:1. More preferably, a polymerictape of the invention has an average cross-sectional aspect ratio of atleast about 20:1, more preferably at least about 50:1, still morepreferably at least about 100:1, still more preferably at least about250:1 and most preferably at least about 400:1.

Each tape is formed from a plurality of multi-filament yarns whereineach yarn includes from 2 to about 1000 filaments, more preferably from30 to 500 filaments, still more preferably from 100 to 500 filaments,still more preferably from about 100 filaments to about 250 filamentsand most preferably from about 120 to about 240 filaments. Multifilamentfibers are also often referred to in the art as bundles of fibers.

Similar to a tape, a “fiber,” a “filament” and a “yarn” as definedherein are each defined as an elongate body the length dimension ofwhich is much greater than the transverse dimensions of width andthickness. The cross-sections of fibers, filaments and yarns may varyand may be regular or irregular, including circular, flat or oblongcross-sections, with substantially circular cross-sections being mostpreferred. Fibers and yarns are distinguished from filaments in thatfibers and yarns are formed from filaments. A fiber may be formed fromjust one filament or from multiple filaments. A fiber formed from justone filament is referred to either as a “single-filament” fiber or a“monofilament” fiber, and a fiber formed from a plurality of filamentsis referred to as a “multi-filament” fiber. However, a “yarn” is definedas a single strand consisting of multiple filaments, analogous to amulti-filament fiber. Such a multi-filament strand is referred to hereinas a “fiber/yarn”.

The processes described herein convert high strength feed fibers/yarns,i.e. fibers/yarns having high ultimate tensile strength (high UTS (hightenacity)) and corresponding low ultimate elongation (UE %), intopolymeric tapes having high UTS and comparatively higher UE % bycompressing, consolidating, and flattening the twisted feed fiber/yarn,thereby forming a polymeric tape with substantial retention offiber/yarn tensile strength. The use of a twisted feed fiber/yarnresults in a tape composed of filaments that are not predominatelyparallel to the centerline of the tape, with the angle between thefilaments and the tape centerline being determined partly by the amountof twist in the feed fiber/yarn, and partly by the tape forming processconditions. It has been discovered that increasing the angle between thefilaments and the tape centerline is a useful way of increasing theultimate elongation of the tape, without significantly reducing theultimate tensile strength of the tape.

In this regard, the high strength fibers/yarns used as feeds for formingthe polymeric tapes herein are preferably fibers/yarns that are suitablefor the manufacture of ballistic resistant composites/fabrics. As usedherein, a “high strength” fiber/yarn is one which has a preferredtenacity of at least about 7 g/denier or more, a preferred tensilemodulus of at least about 150 g/denier or more, a preferred anenergy-to-break of at least about 8 J/g or more, each as measured byASTM D2256. As used herein, the term “denier” refers to the unit oflinear density, equal to the mass in grams per 9000 meters offiber/yarn. As used herein, the term “tenacity” refers to the tensilestress expressed as force (grams) per unit linear density (denier) of anunstressed specimen. The “initial modulus” of a fiber/yarn is theproperty of a material representative of its resistance to deformation.The term “tensile modulus” refers to the ratio of the change intenacity, expressed in grams-force per denier (g/d) to the change instrain, expressed as a fraction of the original fiber/yarn length(in/in).

The feed fibers/yarns may be of any suitable denier. For example, thefeed fibers/yarns may have a denier of from about 50 to about 3000denier, more preferably from about 200 to 3000 denier, still morepreferably from about 1000 to 3000 denier. In another preferredembodiment, the feed fibers/yarns have a denier of from about 650 toabout 2000 denier, more preferably from 800 to 2000 denier, and mostpreferably from about 800 to about 1500 denier. The selection isgoverned by considerations of ballistic effectiveness and cost. Finerfibers/yarns are more costly to manufacture and to weave, but canproduce greater ballistic effectiveness per unit weight.

Preferred fibers/yarns have a preferred tenacity of about 15 g/denier ormore, more preferably about 20 g/denier or more, still more preferablyabout 25 g/denier or more, still more preferably about 30 g/denier ormore, still more preferably about 40 g/denier or more, still morepreferably about 45 g/denier or more, and most preferably about 50g/denier or more. Preferred fibers/yarns also have a preferred tensilemodulus of about 300 g/denier or more, more preferably about 400g/denier or more, more preferably about 500 g/denier or more, morepreferably about 1,000 g/denier or more and most preferably about 1,500g/denier or more. Preferred fibers/yarns also have a preferredenergy-to-break of about 15 J/g or more, more preferably about 25 J/g ormore, more preferably about 30 J/g or more and most preferably have anenergy-to-break of about 40 J/g or more. Methods of forming each of thepreferred feed fiber/yarn types having these combined high strengthproperties are conventionally known in the art.

High tensile strength, high tensile modulus fiber/yarn polymer typesthat are particularly suitable herein include polyolefin fibers/yarns,including high density and low density polyethylene. Particularlypreferred are extended chain polyolefin fibers, such as highly oriented,high molecular weight polyethylene fibers/yarns, particularly ultra-highmolecular weight polyethylene fibers/yarns, and polypropylenefibers/yarns, particularly ultra-high molecular weight polypropylenefibers/yarns. Also suitable are aramid fibers/yarns, particularlypara-aramid fibers/yarns, polyamide fibers/yarns, polyethyleneterephthalate fibers/yarns, polyethylene naphthalate fibers/yarns,extended chain polyvinyl alcohol fibers/yarns, extended chainpolyacrylonitrile fibers/yarns, polybenzoxazole (PBO) fibers/yarns,polybenzothiazole (PBT) fibers/yarns, liquid crystal copolyesterfibers/yarns, glass fibers/yarns, and rigid rod fibers/yarns such as M5®fibers/yarns. M5® fibers/yarns are formed frompyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) and aremanufactured by Magellan Systems International of Richmond, Va. and aredescribed, for example, in U.S. Pat. Nos. 5,674,969, 5,939,553,5,945,537, and 6,040,478, each of which is incorporated herein byreference. Each of these fiber/yarn types described above isconventionally known in the art. Also suitable for producing polymericfibers/yarns are copolymers, block polymers and blends of the abovematerials. For example, the inventive polymeric tapes may be formed frommulti-filament fibers/yarns comprising at least two different filamenttypes, such as two different types of UHMW PE filaments or a blend ofaramid and UHMW PE filaments.

Of these, the most preferred fiber/yarn types include polyethylene,particularly extended chain polyethylene fibers/yarns, aramidfibers/yarns, PBO fibers/yarns, liquid crystal copolyester fibers/yarns,polypropylene fibers/yarns, particularly highly oriented extended chainpolypropylene fibers/yarns, polyvinyl alcohol fibers/yarns,polyacrylonitrile fibers/yarns and rigid rod fibers/yarns, particularlyM5® fibers/yarns.

Specifically most preferred fibers/yarns are ultra high molecular weightpolyethylene (UHMW PE) fibers/yarns. Ultra high molecular weightpolyethylene fibers/yarns are formed from extended chain polyethyleneshaving molecular weights of at least 300,000, preferably at least onemillion and more preferably between two million and five million. Suchextended chain polyethylene fibers/yarns may be grown in solutionspinning processes such as described in U.S. Pat. No. 4,137,394 or4,356,138, which are incorporated herein by reference, or may be spunfrom a solution to form a gel structure, such as described in U.S. Pat.Nos. 4,413,110; 4,536,536; 4,551,296; 4,663,101; 5,006,390; 5,032,338;5,578,374; 5,736,244; 5,741,451; 5,958,582; 5,972,498; 6,448,359;6,746,975; 6,969,553; 7,078,099; 7,344,668 and U.S. patent applicationpublication 2007/0231572, all of which are incorporated herein byreference. Particularly preferred fiber/yarn types are any of thepolyethylene fibers/yarns sold under the trademark SPECTRA® fromHoneywell International Inc, including SPECTRA® 900 fibers/yarns,SPECTRA® 1000 fibers/yarns and SPECTRA® 3000 fibers/yarns, all of whichare commercially available from Honeywell International Inc. ofMorristown, N.J.

The most preferred UHMW PE fibers/yarns selected as a feed for a processof this invention have an intrinsic viscosity when measured in decalinat 135° C. by ASTM D1601-99 of from about 7 dl/g to about 40 dl/g,preferably from about 10 dl/g to about 40 dl/g, more preferably fromabout 12 dl/g to about 40 dl/g, and most preferably, from about 14 dl/gto 35 dl/g. The most preferred UHMW PE fibers/yarns selected as a feedfor a process of this invention are highly oriented and have a c-axisorientation function of at least about 0.96, preferably at least about0.97, more preferably at least about 0.98 and most preferably at leastabout 0.99. The c-axis orientation function is a description of thedegree of alignment of the molecular chain direction with the filamentdirection. A polyethylene filament in which the molecular chaindirection is perfectly aligned with the filament axis would have anorientation function of 1. C-axis orientation function (f_(c)) ismeasured by the wide angle x-ray diffraction method described inCorreale, S. T. & Murthy, Journal of Applied Polymer Science, Vol. 101,447-454 (2006) as applied to polyethylene.

The most preferred UHMW PE fibers/yarns selected as a feed for a processof this invention have a tenacity from about 15 g/d to about 100 g/d,preferably from about 25 g/d to about 100 g/d, more preferably fromabout 30 g/d to about 100 g/d, yet more preferably from about 35 g/d toabout 100 g/d, still more preferably from about 40 g/d to about 100 g/dand most preferably, from about 45 g/d to about 100 g/d.

It is a particular objective of the invention that the polymeric tapesproduced according to a process of the invention have a higher ultimateelongation at high UTS relative to other high UTS tapes. It is generallyknown that increases in fiber/yarn UTS are naturally met with a decreasein fiber/yarn UE %. In order to achieve a tape with a higher UE %, it isnecessary that the feed fibers/yarns are first twisted prior to beingcompressed and flattened into a tape.

Various methods of twisting fibers/yarn are known in the art, and anymethod may be utilized. Useful twisting methods are described, forexample, in U.S. Pat. Nos. 2,961,010; 3,434,275; 4,123,893; 4,819,458and 7,127,879, the disclosures of which are incorporated herein byreference. The fibers/yarns are twisted to have at least about 0.5 turnsof twist per inch of fiber/yarn length up to about 15 twists per inch,more preferably from about 3 twists per inch to about 11 twists per inchof fiber/yarn length. In an alternate preferred embodiment, thefibers/yarns are twisted to have at least 11 twists per inch offiber/yarn length, more preferably from about 11 twists per inch toabout 15 twists per inch of fiber/yarn length. The standard method fordetermining twist in twisted yarns is ASTM D1423-02. Optionally, thefeed fiber/yarn may be heat set by a process described in U.S. Pat. No.4,819,458.

After twisting, the filaments of the twisted feed fiber/yarn mayoptionally be at least partially connected by fusion or by bonding.Fusion of the fiber/yarn filaments may be accomplished by various means,including the use of heat and tension, or through application of asolvent or plasticizing material prior to exposure to heat and tensionas described in U.S. Pat. Nos. 5,540,990; 5,749,214; and 6,148,597,which are hereby incorporated by reference to the extent compatibleherewith. Bonding may be accomplished, for example, by at leastpartially coating the filaments with a resin or other polymeric bindermaterial having adhesive properties, such as apolystyrene-polyisoprene-polystyrene-block copolymer resin commerciallyavailable from Kraton Polymers of Houston, Tex. under the trademarkKRATON® D1107. They may also be thermally bonded together without anadhesive coating. Thermal bonding conditions will depend on the fibertype. When the feed fibers/yarns are coated with a resin or otherpolymeric binder material having adhesive properties to bond thefilaments, only a small amount of the resin/binder is needed. In thisregard, the quantity of resin/binder applied is preferably no more than5% by weight based on the total weight of the filaments plus theresin/binder, such that the filaments comprise at least 95% by weight ofthe coated fiber/yarn based on the total weight of the filaments plusthe resin/binder, and the corresponding tape formed from the yarn willthereby also comprise at least 95% by weight of the component filaments.More preferably, the fibers/yarns and tapes comprise at least about 96%filaments by weight, still more preferably 97% filaments by weight,still more preferably 98% filaments by weight, and still more preferably99% filaments by weight. Most preferably, the fibers/yarns and tapes areresin-free, i.e. are not coated with a bonding resin/binder, and consistessentially of or consist only of filaments.

In accordance with the process of the invention, the twisted andoptionally fused feed fiber/yarn is then compressed, therebyconsolidating the component filaments into a monolithic element andflattening said element into the form of a polymeric tape having apreferred average cross-sectional aspect ratio of at least about 10:1.One useful method for forming such a polymeric tape is described in U.S.patent application Ser. No. 12/539,185, which describes a process forthe continuous production of polyethylene tape articles. Said processcomprises placing a fiber/yarn under a longitudinal tensile force of atleast about 0.25 kilogram-force (2.45 Newtons) and subjecting thefiber/yarn to at least one transverse compression step to flatten,consolidate and compress the fiber/yarn. This transverse compressionstep is preferably conducted at a temperature of from about 25° C. toabout 137° C. while maintaining the longitudinal tensile force on thefiber/yarn, thereby forming a tape article having an averagecross-sectional aspect ratio of at least about 10:1. This compressionstep may optionally be repeated one or more times, preferably at atemperature of from about 100° C. to about 160° C. Thereafter, the tapeis stretched in at least one stage at a temperature in the range of fromabout 130° C. to about 160° C. at a stretch rate of from about 0.001min⁻¹ to about 1 min⁻¹. This stretching step may optionally be repeatedone or more times. During the compression and stretching steps, thelongitudinal tensile force may optionally be increased or decreased, ormay remain constant. Finally, the tape is cooled to a temperature lessthan about 70° C. under tension.

Variations of this process are also described therein. For example, in asecond embodiment, prior to the compression step, the yarns may first beheated to a temperature of from about 100° C. to about 160° C. andstretched at least once at a stretch rate of from about 0.01 min⁻¹ toabout 5 min⁻¹. It should also be understood that the processingtemperatures recited in application Ser. No. 12/539,185 are thepreferred temperatures for compressing and stretching polyethylenemulti-filament yarns having a c-axis orientation function at least 0.96,an intrinsic viscosity when measured in decalin at 135° C. by ASTMD1601-99 of from about 7 dl/g to 40 dl/g, and a tenacity of from about15 g/d to about 100 g/d as measured by ASTM D2256-02. Other polymertypes, such as aramid or PBO fibers/yarns, may have different optimalprocessing conditions. For example, aramid fibers/yarns cannot be fusedtogether in the same way as UHMW PE fibers/yarns because aramidfibers/yarns do not melt and maintain strength. However, aramidfibers/yarns can be fused together by first dissolving the fibersurface, such as with sulfuric acid, followed by pressing the filamentstogether to form a tape. Other fiber types with tape processingconditions similar to aramid fibers/yarns are M5® fibers/yarns, PBO, PBTand all other “liquid crystal” types of fibers/yarns. Fiber types withfusion and tape processing conditions similar to polyethylene fibers arethose formed by melt or solution spinning of thermoplastic polymers,such as PET, nylon, polyvinyl acetate (PVA), polypropylene, etc.

A continuous process of the first embodiment (where the fibers/yarns arenot stretched prior to compression) is illustrated schematically inFIGS. 1, 2 and 7. A continuous process of the second embodiment (wherethe fibers/yarns are heated and stretched prior to compression) isillustrated schematically in FIGS. 3-6. The figures illustrating aparticular embodiment differ in the number and placement of processequipment, but illustrate the same steps. In each of FIGS. 1 to 7, aselected multi-filament UHMW PE fiber/yarn (10-16, respectively) isunwound from a package or beam (not shown) and is passed over and underseveral restraining rolls (20). For polyethylene fibers/yarns, therestraining rolls are at temperature of from about 25° C. to about 137°C.

In FIGS. 1-2 and 7, the fiber/yarn leaving the restraining rolls (80,81, 86, respectively) is passed under tension directly into one or moremeans (30, 33, 39) for compressing, consolidating, and flattening thefiber/yarn, thereby forming a tape. The tape is subsequently heated andstretched at least once. In FIGS. 3-6, the fiber/yarn leaving therestraining rolls (82-85, respectively) is heated and stretched beforebeing compressed. Heating of a yarn may be by any means, such as byinfra-red radiation, contact with a heated surface, or contact with aheated fluid. Preferably, the fiber/yarn is heated and stretched in aforced convection air oven (50-59, 510 in FIGS. 1-7) having multipletemperature zones. For polyethylene fibers/yarns, the fiber/yarn ispreferably stretched at least once at temperatures of from about 100° C.to about 160° C. at a stretch rate of from about 0.01 min⁻¹ to about 5min⁻¹. The stretch rate is defined as the difference between the speedat which a material leaves a stretch zone (V₂) and the speed at which itentered a stretch zone (V₁) divided by the length of the stretch zone(L), i.e.,

Stretch Rate=(V2−V1)/L,min⁻¹

For polyethylene fibers/yarns, the fiber/yarn is preferably stretched toa stretch ratio of from about 1.01:1 to about 20:1 at a temperature ofabout 135° C. to about 155° C. Preferably, the stretch ratio is themaximum possible without rupturing the fiber/yarn, and this will vary aswould be determined by one skilled in the art depending on the polymertype.

In both of the above embodiments, each fiber/yarn or tape is under alongitudinal tensile force at both the outset and conclusion ofcompression in each means for compression (30-40). Longitudinal tensileforce is regulated by regulating the speeds of successive driven means.In one preferred embodiment, the magnitude of the longitudinal tensileforce on the fiber/yarn or tape at the outset of each compression stepis substantially equal to the magnitude of the longitudinal tensileforce on the fiber/yarn or tape at the conclusion of the samecompression step. In the context of the invention, the term“substantially equal” means that the ratio of a lower to higher tensileforce across a compression step is at least 0.75:1, preferably at least0.80:1, more preferably at least 0.85:1, yet more preferably, at least0.90:1, and most preferably, at least 0.95:1. Such substantially equallongitudinal tensile forces at the outset and conclusion of acompression step is a preferred feature of the process because equaltensile forces across a compression step assures zero tension at themidpoint of compression. However, such substantially equal longitudinaltensile forces are not a mandatory processing condition.

At least for polyethylene fibers/yarns, the longitudinal tensile forceis at least 0.25 kilogram-force (abbreviated Kgf, equal to 2.45 Newtons,abbreviated N) on the fiber/yarn or tape at the inlet and at the outletof a compression step. Preferably, the tensile force is at least 0.5 Kgf(4.9 N), more preferably at least 1 Kgf (9.8 N), yet more preferably atleast 2 Kgf (19.6.2 N), and most preferably, at least 4 Kgf (39.2 N) atthe outset and conclusion of a compression step. Most preferably,longitudinal tensile force is as high as possible without rupturing thefiber/yarn or tape and without causing slippage of the fiber/yarn ortape in a compression means.

In the preferred embodiments of invention, the illustrated compressionmeans (30-40) in each of FIGS. 1-7 are counter-rotating, opposed rolls(nip rolls). Each nip roll of a unit preferably has the same surfacespeed, and presses upon the fiber/yarn or tape. Other suitable and wellknown compression means include nip roll stacks consisting of three ormore rolls in a single unit that provide two or more compressions, pairsof moving belts that press from opposite sides against the fiber/yarn ortape, rolls where the fiber/yarn or tape makes a 180° turn under hightension and the like. The pressure applied by nip rolls and moving beltsmay be actuated by hydraulic cylinders or the pressure may result fromfixing a gap between the rolls at a dimension smaller than the thicknessof the incoming material. Still other compression means are possible andare contemplated.

The means for compression may be vibrated. Considering the tape to be aquasi-two dimensional object with length and width but negligiblethickness, the vibration may be in a direction normal to the plane ofthe tape, or in the plane of the tape or in a direction inclined to bothplanes. The vibration may be of low frequency or of sonic or ultra-sonicfrequencies. The vibration may be used as an aid in consolidation byimparting additional pulses of pressure or shear. It may also be used toproduce periodic variations in thickness or width of the compressed tapeuseful for bonding in composite applications.

The pressure exerted in a compression step in each embodiment is fromabout 20 to about 10,000 pounds per square inch (psi) (about 0.14 toabout 69 MPa), preferably from about 50 to about 5000 psi (about 0.34 toabout 34 MPa), and more preferably from about 50 to about 2500 psi(about 0.69 to about 17 MPa). The pressure is preferably increased atsuccessive stages of compression. The compression means are preferablyat a temperature of from about 25° C. to about 160° C., more preferablyfrom about 50° C. to about 155° C., and most preferably from about 100°C. to about 150° C. In the most preferred embodiments where the tapecomprises UHMW PE filaments, the yarns are compressed/flattened intotapes at a temperature of from about 145° C. to about 155° C. and at apressure of from about 2700 to about 3000 psi or greater.

After passage through at least one compression means, e.g. (30) in FIG.1, a now formed tape (100) is preferably heated and stretched at leastonce. Heating of the tape may be by any means, such as by infra-redradiation, contact with a heated surface, or contact with a heatedfluid. Preferably, the tape is heated and stretched in a forcedconvection air oven (50, 51) having multiple temperature zones(demarcated by the dashed lines in the figures). Not shown in thefigures are heaters and blowers that heat and circulate the air throughthe oven.

At least for polyethylene tapes, stretching of the tape is at atemperature of from about 100° C. to about 160° C., and preferably fromabout 135° C. to about 150° C. The tape is stretched at a stretch rateof from about 0.001 min⁻¹ about 1 min⁻¹. Preferably the tape isstretched at a stretch rate of from about 0.001 min⁻¹ to about 0.1min⁻¹. Preferably the tape is stretched to a stretch ratio of from about1.01:1 to 20:1.

The stretching force may be applied by any convenient means such as bypassing the fiber/yarn/tape over and under a sufficient number of drivenrolls (60), as illustrated in FIGS. 2, 3, 4 and 6; by compression means(31,32, 40) as illustrated in FIGS. 1 and 7; by both compression means(36, 37,40) and driven rolls (60, 61) as in FIGS. 5 and 7; or by windingthe fiber/yarn/tape multiple times around a driven godet and idler rollpair (not illustrated). Driven rolls applying the stretching force maybe internal to the oven or outside of the oven.

The longitudinal tensile force need not be the same throughout acontinuous operation. Optionally, a fiber/yarn or tape may be relaxed tolower longitudinal tensile force or permitted to shrink less than about5% between successive compressions or stretches by tension isolationmeans. Alternatively, tension may be increased between successivecompressions or stretches by tension isolation means. In FIG. 7, rolls(61) act as tension isolation means. The tensile force on tape (114)(i.e. tape in a second oven) can be either greater or less than on tape(113) (i.e. tape in a first oven), depending on the speed of nip rolls(39) and (40) and the temperatures in the two ovens. In either case, thespeed of restraining rolls (20) and driven rolls (60) are adjusted tomaintain the tensile force constant across the compression means (39 and40).

The tape is cooled under tension prior to being conveyed to a winder.The length of the tape may diminish slightly due to thermal contraction,but tension should be sufficiently high during cooling to preventshrinkage beyond thermal contraction. Preferably, the tape is cooled onrolls (60) and the rolls are cooled by natural convection, forced air,or are internally water-cooled. The final stretched tape (70-76), cooledunder tension to a temperature less than about 70° C., is wound up undertension (winder not shown) as a package or on a beam.

As noted above, the number and placement of compression and stretchingmeans may be varied within a particular embodiment as is illustratedschematically in the Figures Many other processing sequences consistentwith one of either the first or second embodiments of the invention arepossible, and are contemplated. Preferably, a process of the inventionproduces a tape having a tensile strength of at least 75% of thestrength of the fiber/yarn from which it is made, and more preferablythe tape tenacity is substantially equal to the feeder fiber/yarntenacity. Most preferably, a process of the invention produces a tapehaving a higher tensile strength than the yarn from which it is made. Inthis regard, while fiber/yarn tenacity is measured by ASTM D2256-02 (at10 inch (25.4 cm) gauge length and at an extension rate of 100%/min),tape tensile strength is measured by ASTM D882-09 (at 10 inch (25.4 cm)gauge length and at an extension rate of 100%/min). Typically the tapeUTS will be about 3-5 g/d lower than the feed fiber/yarn. For example,for a feeder fiber/yarn having a UTS of 45 g/denier, the tape UTS couldbe approximately 40 g/denier, or for a 35-37 g/denier UTS fiber/yarn,the tape UTS could be approximately 30-35 g/denier.

Together with twisting of the fiber/yarn, the heating and compressionsteps that form the tape from the twisted fiber/yarn achieve theenhanced UE % of the resulting polymeric tape. In this regard, the UE %of the inventive tapes can be defined in terms of its proportionalrelationship to the UTS. Specifically, the tape UE % can be defined bythe following formula:

y=−0.04x+b

where y is the ultimate elongation (measured in %), wherein x is theultimate tensile strength (measured in g/denier) of the tape, where b=5or greater, and where x (UTS) is 15 g/denier or greater, more preferablyx is 20 g/denier or greater, still more preferably x is 22 g/denier orgreater, still more preferably where x is 25 g/denier or greater, stillmore preferably where x is 30 g/denier or greater, still more preferablywhere x is 35 g/denier or greater, still more preferably where x is 40g/denier or greater, still more preferably where x is 45 g/denier orgreater, still more preferably where x is 50 g/denier or greater, stillmore preferably where x is 55 g/denier or greater, still more preferablywhere x is 60 g/denier or greater, still more preferably where x is 65g/denier or greater, still more preferably where x is 70 g/denier orgreater, and still more preferably where x is 75 g/denier or greater.This relationship is illustrated in FIG. 8. Polymeric tapes achievingthese properties will be formed from fibers/yarns that have been twistedat least about 0.5 turns of twist per inch of fiber/yarn length up toabout 15 twists per inch. Accordingly, the b value, i.e. the value wherethe line plotted in FIG. 8 would cross the y-axis, will range from 5 to15. Alternative ranges for the b value are 5.5 to 15, 6.0 to 15, 7.0 to15, 7.5 to 15, 8.0 to 15, 8.5 to 15, 9.0 to 15, 9.5 to 15 and 10 to 15,as well as alternatively 5.5 to 13, 6.0 to 13, 7.0 to 13, 7.5 to 13, 8.0to 13, 8.5 to 13, 9.0 to 13, 9.5 to 13 and 10 to 13; or alternatively5.5 to 10, 6.0 to 10, 7.0 to 10, 7.5 to 10, 8.0 to 10, 8.5 to 10, 9.0 to10, and 9.5 to 10. It is also most preferred, though not required, thatthe polymeric tapes of the invention have a UE % of at least 5.0%, suchthat y=at least 5.0(%), with an expected maximum UE of 15.0%.

FIG. 9 is a bar graph illustrating the relationship between UTS and UE %for the inventive polymeric tapes from a different perspective, whereinthe tapes have an ultimate tensile strength of at least 15 g/denier andwherein the product of the ultimate tensile strength (g/denier) of thetape and the ultimate elongation (%) of the tape (UTS*UE) is at least150. More preferably, the UTS*UE value is at least about 160, still morepreferably at least about 170, still more preferably at least about 180,still more preferably at least about 190, and most preferably the UTS*UEvalue is at least about 200. For example, a tape having a UTS of 15g/denier and a UE % of 10% will have a UTS*UE value of 150. A tapehaving a UTS of 40 g/denier and a UE % of 4.0% will have a UTS*UE valueof 160. As stated above, the UE % is controlled partially by the twistamount of the pre-compressed fiber/yarn, as well as the natural UE % ofthe polymeric feed fiber/yarn. The achievable twist amount depends tosome degree on the fiber/yarn denier. For example, tapes formed fromuntwisted SPECTRA® UHMW PE fibers/yarns identified in ComparativeExamples 1-4 having tenacities ranging from 23.9 g/denier to 40.9g/denier have ultimate elongations ranging from about 3.2 to about 9.The data plotted in FIG. 9 is outlined in Table 1, and additionalexamples are provided in the Examples section below.

The polymeric tapes produced according to the processes of the inventionmay be fabricated into woven and/or non-woven fabric materials that havesuperior ballistic penetration resistance. For the purposes of theinvention, articles that have superior ballistic penetration resistancedescribe those which exhibit excellent properties against deformableprojectiles, such as bullets, and against penetration of fragments, suchas shrapnel.

The inventive polymeric tapes may be fabricated into wovenfabrics/composites and non-woven fabrics/composites according to thesame techniques that may be employed when fabricating woven andnon-woven fabrics/composites from fibers/yarns rather than tapes. Forexample, in a preferred embodiment herein, a non-woven fabric ispreferably formed by stacking one or more plies of randomly orientedpolymeric tapes (e.g. a felt or a mat construction) or unidirectionallyaligned, parallel polymeric tapes, and then consolidating the stack toform a tape layer. In this regard, a “tape layer” as used herein maycomprise a single-ply of non-woven tapes or a plurality of non-woventape plies. A tape layer may also comprise a woven fabric or a pluralityof consolidated woven fabrics. A “layer” describes a generally planararrangement having both an outer top surface and an outer bottomsurface. A single “ply” of unidirectionally oriented tapes comprises anarrangement of generally non-overlapping tapes that are aligned in aunidirectional, substantially parallel array, and is also known in theart as a “unitape”, “unidirectional tape”, “UD” or “UDT.” As usedherein, an “array” describes an orderly arrangement of tapes, which isexclusive of woven fabrics. A “parallel array” describes an orderlyparallel arrangement of tapes where the tapes are arrangedunidirectionally in a side-by-side, substantially parallel, planarrelation to each other, most typically such that only their edges are incontact with each other. A UD or UDT layer/ply is a laminate formed bylaminating (consolidating) these substantially parallel tapes together.The term “oriented” as used in the context of “oriented tapes” refers tothe alignment of the tapes as opposed to stretching of the tapes.

As used herein, “consolidating” refers to combining a plurality of tapelayers or plies into a single unitary structure, with or without theassistance of a polymeric binder material. Consolidation can occur viadrying, cooling, heating, pressure or a combination thereof. Heat and/orpressure may not be necessary, as the tapes or tape layers/plies mayjust be glued together, as is the case in a wet lamination process. Theterm “composite” refers to combinations of tapes, optionally with aleast one polymeric binder material. As stated above, this polymericbinder material may be an adhesive used to bond the yarn filamentstogether before or during the compression step. A “complex composite”refers to a consolidated combination of a plurality of tape layers.

As described herein, “non-woven” fabrics include all fabric structuresthat are not formed by weaving. For example, non-woven fabrics maycomprise a plurality of unitapes that are optionally at least partiallycoated with a polymeric binder material, stacked/overlapped andconsolidated into a single-layer, monolithic element. Non-woven fabricsmay also comprise felts or mats that comprise non-parallel, randomlyoriented tapes that are optionally coated with a polymeric bindercomposition.

Generally, a polymeric binder coating, also commonly known in the art asa “polymeric matrix” material, is necessary to efficiently merge, i.e.consolidate, a plurality of non-woven plies/layers formed fromyarns/fibers. A similar polymeric binder coating may be used whenforming non-woven plies/layers from polymeric tapes. However, due to theunique process used to form the polymeric tapes where fibers/yarns arecompressed at high temperatures and pressures, it is a unique feature ofthis invention that a binder/matrix coating is optional and notrequired. The flat structure of the tapes allows them to be merelyhot-pressed together with sufficient bonding according to theconsolidation conditions described herein. When the tapes are formedinto woven fabrics, coating the woven fabrics with a polymeric bindermaterial may be desired when it is desired to consolidate a plurality ofstacked woven fabrics into a complex composite. However, a stack ofwoven fabrics may be may be attached by other means as well, such aswith a conventional adhesive layer or by stitching.

To the extent that a resin is used, ballistic resistant articles may beconsolidated with a lower quantity of binder/matrix resin than istypically needed for forming articles from uncompressed yarns becausethe resin need only be applied as a surface layer without impregnatingor coating the individual component filaments of the tape to promotebonding of a tape layer to another layer of the tape. Accordingly, thetotal weight of the binder/matrix coating in a composite preferablycomprises from about 0% to about 10%, still more preferably from about0% to about 5% by total weight of the component filaments plus theweight of the coating. Even more preferably, ballistic resistantarticles of the invention comprise from about 0% to about 2% by weightof a binder/matrix coating, or about 0% to about 1% by weight, or onlyabout 1% to about 2% by weight. Most preferably, both woven andnon-woven ballistic resistant articles fabricated from the polymerictapes of the invention are entirely resin-free as described incommonly-owned U.S. patent application Ser. No. 61/570,071, which isincorporated herein by reference to the extent consistent herewith.

Even when a polymeric matrix/binder material is not needed for itsadhesive properties, such a coating may also be desirable to provide afabric with other properties, such as abrasion resistance and resistanceto deleterious environmental conditions, so it may still be desirable tocoat the tapes with such a binder material. In this regard, when used apolymeric binder material will partially or substantially coat theindividual tapes of the tape layers. Suitable polymeric binder materialsinclude both low modulus materials and high modulus materials. Lowmodulus polymeric matrix binder materials generally have a tensilemodulus of about 6,000 psi (41.4 MPa) or less according to ASTM D638testing procedures and are typically employed for the fabrication ofsoft, flexible armor, such as ballistic resistant vests. High modulusmaterials generally have a higher initial tensile modulus than 6,000 psiand are typically employed for the fabrication of rigid, hard armorarticles, such as helmets.

A low modulus elastomeric material preferably has a tensile modulus ofabout 4,000 psi (27.6 MPa) or less, more preferably about 2400 psi (16.5MPa) or less, still more preferably 1200 psi (8.23 MPa) or less, andmost preferably is about 500 psi (3.45 MPa) or less. The glasstransition temperature (Tg) of the low modulus elastomeric material ispreferably less than about 0° C., more preferably the less than about−40° C., and most preferably less than about −50° C. A low moduluselastomeric material also has a preferred elongation to break of atleast about 50%, more preferably at least about 100% and most preferablyhas an elongation to break of at least about 300%.

Representative examples include polybutadiene, polyisoprene, naturalrubber, ethylene-propylene copolymers, ethylene-propylene-dieneterpolymers, polysulfide polymers, polyurethane elastomers,chlorosulfonated polyethylene, polychloroprene, plasticizedpolyvinylchloride, butadiene acrylonitrile elastomers,poly(isobutylene-co-isoprene), polyacrylates, polyesters, polyethers,fluoroelastomers, silicone elastomers, copolymers of ethylene,polyamides (useful with some filament types), acrylonitrile butadienestyrene, polycarbonates, and combinations thereof, as well as other lowmodulus polymers and copolymers curable below the melting point of thefilaments forming the tapes. Also preferred are blends of differentelastomeric materials, or blends of elastomeric materials with one ormore thermoplastics.

Particularly useful are block copolymers of conjugated dienes and vinylaromatic monomers. Butadiene and isoprene are preferred conjugated dieneelastomers. Styrene, vinyl toluene and t-butyl styrene are preferredconjugated aromatic monomers. Block copolymers incorporatingpolyisoprene may be hydrogenated to produce thermoplastic elastomershaving saturated hydrocarbon elastomer segments. The polymers may besimple tri-block copolymers of the type A-B-A, multi-block copolymers ofthe type (AB)_(n) (n=2-10) or radial configuration copolymers of thetype R-(BA)_(x) (x=3-150); wherein A is a block from a polyvinylaromatic monomer and B is a block from a conjugated diene elastomer.Many of these polymers are produced commercially by Kraton Polymers ofHouston, Tex. and described in the bulletin “Kraton ThermoplasticRubber”, SC-68-81. Also useful are resin dispersions ofstyrene-isoprene-styrene (SIS) block copolymer sold under the trademarkPRINLIN® and commercially available from Henkel Technologies, based inDüsseldorf, Germany. Particularly preferred low modulus polymeric binderpolymers comprise styrenic block copolymers sold under the trademarkKRATON® commercially produced by Kraton Polymers. A particularlypreferred polymeric binder material comprises apolystyrene-polyisoprene-polystyrene-block copolymer sold under thetrademark KRATON®.

Also particularly preferred are acrylic polymers and acrylic copolymers.Acrylic polymers and copolymers are preferred because their straightcarbon backbone provides hydrolytic stability. Acrylic polymers are alsopreferred because of the wide range of physical properties available incommercially produced materials. Preferred acrylic polymersnon-exclusively include acrylic acid esters, particularly acrylic acidesters derived from monomers such as methyl acrylate, ethyl acrylate,n-propyl acrylate, 2-propyl acrylate, n-butyl acrylate, 2-butyl acrylateand tert-butyl acrylate, hexyl acrylate, octyl acrylate and 2-ethylhexylacrylate. Preferred acrylic polymers also particularly includemethacrylic acid esters derived from monomers such as methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, 2-propylmethacrylate, n-butyl methacrylate, 2-butyl methacrylate, tert-butylmethacrylate, hexyl methacrylate, octyl methacrylate and 2-ethylhexylmethacrylate. Copolymers and terpolymers made from any of theseconstituent monomers are also preferred, along with those alsoincorporating acrylamide, n-methylol acrylamide, acrylonitrile,methacrylonitrile, acrylic acid and maleic anhydride. Also suitable aremodified acrylic polymers modified with non-acrylic monomers. Forexample, acrylic copolymers and acrylic terpolymers incorporatingsuitable vinyl monomers such as: (a) olefins, including ethylene,propylene and isobutylene; (b) styrene, N-vinylpyrrolidone andvinylpyridine; (c) vinyl ethers, including vinyl methyl ether, vinylethyl ether and vinyl n-butyl ether; (d) vinyl esters of aliphaticcarboxylic acids, including vinyl acetate, vinyl propionate, vinylbutyrate, vinyl laurate and vinyl decanoates; and (f) vinyl halides,including vinyl chloride, vinylidene chloride, ethylene dichloride andpropenyl chloride. Vinyl monomers which are likewise suitable are maleicacid diesters and fumaric acid diesters, in particular of monohydricalkanols having 2 to 10 carbon atoms, preferably 3 to 8 carbon atoms,including dibutyl maleate, dihexyl maleate, dioctyl maleate, dibutylfumarate, dihexyl fumarate and dioctyl fumarate.

Most specifically preferred are polar resins or polar polymer,particularly polyurethanes within the range of both soft and rigidmaterials at a tensile modulus ranging from about 2,000 psi (13.79 MPa)to about 8,000 psi (55.16 MPa). Preferred polyurethanes are applied asaqueous polyurethane dispersions that are most preferably co-solventfree. Such includes aqueous anionic polyurethane dispersions, aqueouscationic polyurethane dispersions and aqueous nonionic polyurethanedispersions. Particularly preferred are aqueous anionic polyurethanedispersions, and most preferred are aqueous anionic, aliphaticpolyurethane dispersions. Such includes aqueous anionic polyester-basedpolyurethane dispersions; aqueous aliphatic polyester-based polyurethanedispersions; and aqueous anionic, aliphatic polyester-based polyurethanedispersions, all of which are preferably cosolvent free dispersions.Such also includes aqueous anionic polyether polyurethane dispersions;aqueous aliphatic polyether-based polyurethane dispersions; and aqueousanionic, aliphatic polyether-based polyurethane dispersions, all ofwhich are preferably cosolvent free dispersions. Similarly preferred areall corresponding variations (polyester-based; aliphaticpolyester-based; polyether-based; aliphatic polyether-based, etc.) ofaqueous cationic and aqueous nonionic dispersions. Most preferred is analiphatic polyurethane dispersion having a modulus at 100% elongation ofabout 700 psi or more, with a particularly preferred range of 700 psi toabout 3000 psi. More preferred are aliphatic polyurethane dispersionshaving a modulus at 100% elongation of about 1000 psi or more, and stillmore preferably about 1100 psi or more. Most preferred is an aliphatic,polyether-based anionic polyurethane dispersion having a modulus of 1000psi or more, preferably 1100 psi or more.

Preferred high modulus binder materials include polyurethanes (bothether and ester based), epoxies, polyacrylates, phenolic/polyvinylbutyral (PVB) polymers, vinyl ester polymers, styrene-butadiene blockcopolymers, as well as mixtures of polymers such as vinyl ester anddiallyl phthalate or phenol formaldehyde and polyvinyl butyral. Aparticularly preferred rigid polymeric binder material for use in thisinvention is a thermosetting polymer, preferably soluble incarbon-carbon saturated solvents such as methyl ethyl ketone, andpossessing a high tensile modulus when cured of at least about 1×10⁶ psi(6895 MPa) as measured by ASTM D638. Particularly preferred rigidpolymeric binder materials are those described in U.S. Pat. No.6,642,159, the disclosure of which is incorporated herein by reference.The rigidity, impact and ballistic properties of the articles formedfrom the composites of the invention are affected by the tensile modulusof the polymeric binder polymer coating the tapes. The polymeric binder,whether a low modulus material or a high modulus material, may alsoinclude fillers such as carbon black or silica, may be extended withoils, or may be vulcanized by sulfur, peroxide, metal oxide or radiationcure systems as is well known in the art.

A polymeric matrix/binder may be applied either simultaneously orsequentially to a plurality of tapes, which may be arranged as a web oras an array, to thereby form a coated web/array. The matrix/binder mayalso be applied to an already woven fabric to form a coated wovenfabric, or as another arrangement, to thereby coat the tape layers withthe matrix/binder. The polymeric binder material may be applied onto theentire surface area of the individual tapes or only onto a partialsurface area of the tapes, but most preferably the polymeric bindermaterial is applied onto substantially all the surface area of eachindividual polymeric tape forming a tape layer of the invention.

The polymeric material may also be applied onto tapes prior to weavingthe coated tapes into a woven fabric or prior to forming the tapes intoa tape layer. Techniques of forming woven fabrics are well known in theart and any fabric weave may be used, such as plain weave, crowfootweave, basket weave, satin weave, twill weave and the like. Plain weaveis most common, where tapes are woven together in an orthogonal 0°/90°orientation. Also useful are 3D weaving methods wherein multi-layerwoven structures are fabricated by weaving warp and weft tape threadsboth horizontally and vertically.

Techniques for forming non-woven fabrics from fibers/yarns are wellknown in the art, and those techniques apply similarly to the inventivepolymeric tapes. In a typical process, a plurality of tapes are arrangedinto at least one array, typically being arranged as a tape webcomprising a plurality of tapes aligned in a substantially parallel,unidirectional array. The tapes may then be coated with a bindermaterial if desired, and the coated tapes are then formed into non-woventape plies, i.e. unitapes. If a binder material is not used, tape-basedunitapes may be formed, for example, by lining up the tapes side-by-sidein a substantially parallel array, followed by pressing the array withheat and pressure to bond the tapes together into a sheet. This sheetmay then be trimmed into the desired size to form one or more tape-basedunitape plies. In another embodiment, continuous tapes may be woundaround a plate, such as described in commonly-owned U.S. Pat. No.5,135,804, followed by inserting the plate into a press and pressing itwith heat and/or pressure to bond the tapes together, after which thebound tapes may be cut or trimmed. U.S. Pat. No. 5,135,804, which isincorporated by reference herein, teaches winding fibers around a 3-inchsquare metal plate. For the purposes of this invention, the metal plateemployed may be any size and is not limited to a 3-inch square. Thisprocess may also be employed by winding tapes around the plate inmultiple directions to form a multi-ply structure.

To form a multi-ply, non-woven tape layer, a plurality of unitapesformed by any method are then overlapped atop each other andconsolidated into single-layer, monolithic element, most preferablywherein the parallel tapes of each single-ply are positionedorthogonally to the parallel tapes of each adjacent single-ply, relativeto the direction of the central longitudinal axis of the tapes in a tapeply. Although orthogonal 0°/90° tape orientations are preferred,adjacent plies can be aligned at virtually any angle between about 0°and about 90° with respect to the central longitudinal axis of anothertape ply. For example, a five ply non-woven structure may have pliesoriented at a 0°/45°/90°/45°/0° or at other angles, such as rotations ofadjacent plies/layers in 15° or 30° increments. Such rotatedunidirectional alignments are described, for example, in U.S. Pat. Nos.4,457,985; 4,748,064; 4,916,000; 4,403,012; 4,623,574; and 4,737,402,all of which are incorporated herein by reference to the extent notincompatible herewith.

The stack of overlapping, non-woven tape plies is consolidated eitherunder heat and pressure or by adhering the coatings of individual tapeplies to each other to form a non-woven composite fabric. Non-woven tapelayers or fabrics preferably include from 1 to about 6 adjoined tapeplies, but may include as many as about 10 to about 20 plies as may bedesired for various applications. The greater the number of pliestranslates into greater ballistic resistance, but also greater weight.

Methods useful for consolidating tape plies to form tape layers andcomposites are well known from the art of fibers/yarns, such as by themethods described in U.S. Pat. No. 6,642,159. Consolidation can occurvia drying, cooling, heating, pressure or a combination thereof. Heatand/or pressure may not be necessary, as the tape layers may just beglued together, as is the case in a wet lamination process. Typically,consolidation is done by positioning the individual tape plies on oneanother under conditions of sufficient heat and pressure to cause theplies to combine into a unitary article. Consolidation may be done attemperatures ranging from about 50° C. to about 175° C., preferably fromabout 105° C. to about 175° C., and at pressures ranging from about 5psig (0.034 MPa) to about 2500 psig (17 MPa), for from about 0.01seconds to about 24 hours, preferably from about 0.02 seconds to about 2hours. When heating, it is possible that the polymeric binder coatingcan be caused to stick or flow without completely melting. However,generally, if the polymeric binder material is caused to melt,relatively little pressure is required to form the composite, while ifthe binder material is only heated to a sticking point, more pressure istypically required. As is conventionally known in the art, consolidationmay be conducted in a calender set, a flat-bed laminator, a press or inan autoclave. Consolidation may also be conducted by vacuum molding thematerial in a mold that is placed under a vacuum. Vacuum moldingtechnology is well known in the art. Most commonly, a plurality oforthogonal tape webs are “glued” together with a small amount of binderpolymer (<5% by weight) and run through a flat bed laminator to improvethe uniformity and strength of the bond. Further, the consolidation andpolymer application/bonding steps may comprise two separate steps or asingle consolidation/lamination step.

Alternately, consolidation may be achieved by molding under heat andpressure in a suitable molding apparatus. Generally, molding isconducted at a pressure of from about 50 psi (344.7 kPa) to about 5,000psi (34,470 kPa), more preferably about 100 psi (689.5 kPa) to about3,000 psi (20,680 kPa), most preferably from about 150 psi (1,034 kPa)to about 1,500 psi (10,340 kPa). Molding may alternately be conducted athigher pressures of from about 5,000 psi (34,470 kPa) to about 15,000psi (103,410 kPa), more preferably from about 750 psi (5,171 kPa) toabout 5,000 psi, and more preferably from about 1,000 psi to about 5,000psi. The molding step may take from about 4 seconds to about 45 minutes.Preferred molding temperatures range from about 200° F. (˜93° C.) toabout 350° F. (˜177° C.), more preferably at a temperature from about200° F. to about 300° F. and most preferably at a temperature from about200° F. to about 280° F. The pressure under which the tape layers andfabric composites of the invention are molded has a direct effect on thestiffness or flexibility of the resulting molded product. Particularly,the higher the pressure at which they are molded, the higher thestiffness, and vice-versa. In addition to the molding pressure, thequantity, thickness and composition of the tape plies and polymericbinder coating type also directly affects the stiffness of the articlesformed from the composites.

While each of the molding and consolidation techniques described hereinare similar, each process is different. Particularly, molding is a batchprocess and consolidation is a generally continuous process. Further,molding typically involves the use of a mold, such as a shaped mold or amatch-die mold when forming a flat panel, and does not necessarilyresult in a planar product. Normally consolidation is done in a flat-bedlaminator, a calendar nip set or as a wet lamination to produce soft(flexible) body armor fabrics. Molding is typically reserved for themanufacture of hard armor, e.g. rigid plates. In either process,suitable temperatures, pressures and times are generally dependent onthe type of polymeric binder coating materials, polymeric bindercontent, process used and fiber/yarn type used to fabricate thepolymeric tapes.

The tape layers or composites may also optionally comprise one or morethermoplastic polymer layers attached to one or both of the outersurfaces of the layer or composite. Suitable polymers for thethermoplastic polymer layer non-exclusively include polyolefins,polyamides, polyesters (particularly polyethylene terephthalate (PET)and PET copolymers), polyurethanes, vinyl polymers, ethylene vinylalcohol copolymers, ethylene octane copolymers, acrylonitrilecopolymers, acrylic polymers, vinyl polymers, polycarbonates,polystyrenes, fluoropolymers and the like, as well as co-polymers andmixtures thereof, including ethylene vinyl acetate (EVA) and ethyleneacrylic acid. Also useful are natural and synthetic rubber polymers. Ofthese, polyolefin and polyamide layers are preferred. The preferredpolyolefin is a polyethylene. Non-limiting examples of usefulpolyethylenes are low density polyethylene (LDPE), linear low densitypolyethylene (LLDPE), medium density polyethylene (MDPE), linear mediumdensity polyethylene (LMDPE), linear very-low density polyethylene(VLDPE), linear ultra-low density polyethylene (ULDPE), high densitypolyethylene (HDPE) and co-polymers and mixtures thereof. Also usefulare SPUNFAB® polyamide webs commercially available from Spunfab, Ltd, ofCuyahoga Falls, Ohio (trademark registered to Keuchel Associates, Inc.),as well as THERMOPLAST™ and HELIOPLAST™ webs, nets and films,commercially available from Protechnic S.A. of Cernay, France. Such athermoplastic polymer layer may be bonded to the tape layer/compositesurfaces using well known techniques, such as thermal lamination.Typically, laminating is done by positioning the individual layers onone another under conditions of sufficient heat and pressure to causethe layers to combine into a unitary structure.

Lamination may be conducted at temperatures ranging from about 95° C. toabout 175° C., preferably from about 105° C. to about 175° C., atpressures ranging from about 5 psig (0.034 MPa) to about 100 psig (0.69MPa), for from about 5 seconds to about 36 hours, preferably from about30 seconds to about 24 hours. Such thermoplastic polymer layers mayalternatively be bonded to the outer surfaces with hot glue or hot meltfibers as would be understood by one skilled in the art.

To produce a ballistic resistant article from the polymeric tapes of theinvention having sufficient ballistic resistance properties, the totalweight of the binder/matrix coating in a composite preferably comprisesfrom about 0% to about 10% by weight, more preferably from about 0% toabout 7%, and most preferably from about 0% to about 5% by weight of thefilaments (which form the tapes) plus the weight of the coating.

The thickness of the tape layers will correspond to the thickness of theindividual tapes and the number of tape plies incorporated into thematerial. For example, a preferred woven fabric will have a preferredthickness of from about 25 μm to about 600 μm per ply/layer, morepreferably from about 50 μm to about 385 μm and most preferably fromabout 75 μm to about 255 μm per ply/layer. A preferred two-ply non-wovenfabric will have a preferred thickness of from about 12 μm to about 600μm, more preferably from about 50 μm to about 385 μm and most preferablyfrom about 75 μm to about 255 μm. Any thermoplastic polymer layers arepreferably very thin, having preferred layer thicknesses of from about 1μm to about 250 μm, more preferably from about 5 μm to about 25 μm andmost preferably from about 5 μm to about 9 μm. Discontinuous webs suchas SPUNFAB® non-woven webs are preferably applied with a basis weight of6 grams per square meter (gsm). While such thicknesses are preferred, itis to be understood that other thicknesses may be produced to satisfy aparticular need and yet fall within the scope of the present invention.

Articles of the invention may be formed from tape layers or compositesthat comprise only one type of tape or that comprise a hybrid structureincluding more than one type of tape. For example, an article may befabricated from at least two different polymeric tape types wherein afirst tape type has a first number of twists per inch of yarn length anda second tape type has a second number of twists per inch of yarnlength, wherein the first number of twists and the second number oftwists per inch of yarn length are different. Alternatively, an articlemay be fabricated from at least two different polymeric tape types whereeach polymeric tape type has the same number of twists per inch of yarnlength, but where the tapes comprise different filament polymer types,such as a combination of UHMW PE tapes and aramid tapes. In yet anotheralternative embodiment, an article may be fabricated from a combinationof tapes that were thermally bonded together before compression, andtapes that were adhesively bonded together before compression.

The fabrics of the invention may be used in various applications to forma variety of different ballistic resistant articles using well knowntechniques, including flexible, soft armor articles as well as rigid,hard armor articles. For example, suitable techniques for formingballistic resistant articles are described in, for example, U.S. Pat.Nos. 4,623,574, 4,650,710, 4,748,064, 5,552,208, 5,587,230, 6,642,159,6,841,492 and 6,846,758, all of which are incorporated herein byreference to the extent not incompatible herewith. The composites areparticularly useful for the formation of hard armor and shaped orunshaped sub-assembly intermediates formed in the process of fabricatinghard armor articles. By “hard” armor is meant an article, such ashelmets, panels for military vehicles, or protective shields, which havesufficient mechanical strength so that it maintains structural rigiditywhen subjected to a significant amount of stress and is capable of beingfreestanding without collapsing. Such hard articles are preferably, butnot exclusively, formed using a high tensile modulus binder material.

The structures can be cut into a plurality of discrete sheets andstacked for formation into an article or they can be formed into aprecursor which is subsequently used to form an article. Such techniquesare well known in the art. In a most preferred embodiment of theinvention, a tape composite comprising a plurality of tape layers/pliesis provided wherein a thermoplastic polymer is bonded to at least oneouter surface of each tape layer/ply either before, during or after aconsolidation step which consolidates the plurality of tapelayers/plies, wherein the plurality of tape layers/plies aresubsequently merged by another consolidation step which consolidates theplurality of tape layers into an armor article or sub-assembly of anarmor article.

The following examples serve to illustrate the invention.

Example 1

A 1200 denier SPECTRA® 900 multi-filament UHMW PE yarn was twisted inthe S-direction to form a twisted yarn having 7 turns per inch (TPI)(2.76 turns/cm). The tenacity of this S-twisted yarn was approximately30-32 g/denier. This was repeated with a second 1200 denier SPECTRA® 900multi-filament UHMW PE yarn, and the two S-twisted 7 TPI yarns were thencabled together in the Z-direction with 5 turns per inch (1.97 turns/cm)to form a 2400 denier cabled yarn. This cabled yarn was thensimultaneously drawn and fused according to the techniques described incommonly-owned U.S. Pat. No. 7,966,797, which is incorporated herein byreference to the extent consistent herewith. Drawing and fusing for thisexample was conducted at 155.5° C. in a 24 meter long oven at a drawratio of 2.66 (15 meters/min feed speed; 40 meters/min take up speed).

The heating and drawing step transforms the multi-filament cabled yarninto a fused monofilament-like yarn, where the “monofilament-like” meansthat the multiple filaments comprising the yarns are fused together atleast to some degree, giving the yarn a monofilament or substantiallymonofilament appearance and feel. The resulting monofilament-like yarnhad a denier of 1053, an ultimate elongation (UE %) of 4.05% and atenacity (UTS) of 28.1 g/denier.

The monofilament-like drawn/fused cabled yarn was then cold pressed,i.e. flattened between two rolls at room temperature (70-72° F.) (21-22°C.) according to the methods described in U.S. patent application Ser.No. 12/539,185, thereby forming a polymeric tape having a UTS of 22.5g/d, a UE % of 7.3% and a denier of 1114.

Example 2

A 2400 denier SPECTRA® 900 multi-filament UHMW PE yarn (2×1200 denierSPECTRA® 900 multifilament UHMW PE yarns) was twisted into a 7 TPItwisted yarn. Unlike Example 1, the two 1200 denier yarns forming thecombined 2400 denier yarn of this example was not cabled. The 2400denier yarn was then simultaneously drawn and fused in a 24 meter longoven as in Example 1, thereby forming a fused monofilament-like yarn.The UTS of the monofilament-like yarn was 29.7 g/d. The UE % was 4.09%and the denier was 1061. This monofilament-like yarn was then coldpressed and flattened between two rolls at room temperature according tothe methods described in U.S. patent application Ser. No. 12/539,185,thereby forming a polymeric tape having a UTS of 25.5 g/d, a UE % of9.24%, and a denier of 1072.

Example 3

Example 1 was repeated thereby forming a polymeric tape having a UTS of24.5 g/denier, a UE % of 6.32% and a denier of 1043.

Example 4

Example 2 was repeated thereby forming a polymeric tape having a UTS of25.6 g/denier, a UE % of 6.39% and a denier of 1045.

Example 5

A 2400 denier SPECTRA® 900 multi-filament UHMW PE yarn (2×1200 denierSPECTRA® 900 multifilament UHMW PE yarns) is twisted into an 11 TPI(4.33 turns/cm) twisted yarn. The twisted yarn is then simultaneouslydrawn and fused in a 24 meter long oven as in Examples 1-4 at 155.5° C.with a draw ratio of 2.66, thereby forming a fused monofilament-likeyarn. The monofilament-like yarn is then cold pressed and flattened atroom temperature as in Examples 1-4, thereby forming a polymeric tapehaving a UTS of 22 g/d, a UE % of 10% and a denier of 1100.

Example 6

Example 5 is repeated except that the 2400 denier SPECTRA® 900 yarn istwisted into a 7 TPI twisted yarn, and the monofilament-like yarn formedtherefrom is hot pressed/flattened into a tape at 150° C. rather thancold pressed/flattened into a tape at room temperature (21-22° C.). Theresulting polymeric tape has a UTS of 24 g/d, a UE % of 11% and a denierof 1100.

Comparative Examples 1-7

The polymeric tapes of inventive Examples 1-4 are compared to otherknown polymeric tapes having the properties outlined in Table 1 below.Comparative Examples 1-3 present the properties of tapes formed bydrawing, fusing and flattening untwisted multifilament UHMW PE yarnsthat are analogous to the feeder yarns of inventive Examples 1-3 butwithout being twisted. Comparative Example 4 identifies the knownproperties of a tape formed according to U.S. Pat. No. 4,623,574.Comparative Example 5 identifies the known properties of polyethylenetapes commercially available from Teijin Fibers Ltd. under the trademarkENDUMAX® TA23. Comparative Example 6 identifies the known properties ofpolyethylene tapes commercially available from DuPont under thetrademark TENSYLON® HT1900. Comparative Example 7 identifies the knownproperties of polyethylene tapes commercially available from DSM asdescribed in their U.S. patent application publication no. 2008/0156345.

The data summarized in Table 1 below is further illustrated in FIGS. 8and 9. Specifically, FIG. 8 is a graphic representation illustrating therange of the curve defined by the formula y=−0.04x+b, where b=5 andwhere b=15, and how the data for Comparative Examples 1-7 relates tothis curve. FIG. 9 is a graphic representation illustrating the UTS*UE %data presented in Table 1 for inventive Examples 1-4 and ComparativeExamples 1-7.

TABLE 1 UTS Example (g/denier) UE % UTS*UE % 1 22.5 7.28 163.8 2 25.59.24 235.62 3 24.5 6.32 154.84 4 25.6 6.39 163.584 Comp. 1 34.4 3.25 118Comp. 2 40.9 3.29 134.5 Comp. 3 29 3.6 104.4 Comp. 4 23.9 3.8 90.82Comp. 5 25.3 1.75 44.3 Comp. 6 19.5 1.9 37.05 Comp. 7 41.5 3.2 132.7

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove and all equivalents thereto.

1-20. (canceled)
 21. A process for forming a layer comprising aplurality of polymeric tapes, the method comprising: a) providing aplurality of polymeric tapes, each polymeric tape comprising a flattenedmulti-filament yarn, each of said yarns comprising a plurality ofcontinuous polymeric filaments; b) arranging said plurality of polymerictapes into a side-by-side planar array such that only their edges are incontact with each other; c) optionally applying a polymeric bindermaterial onto said array of tapes; and d) applying heat and/or pressureto said array of tapes under conditions sufficient to consolidate saidarray of tapes into a substantially planar, unitary layer.
 22. Theprocess of claim 21 wherein step c) is conducted.
 23. A process forforming a multi-layer article comprising performing steps a)-d) of claim21 at least twice to thereby form a plurality of layers, arranging saidplurality of layers into a stack, and thereafter applying heat and/orpressure to said stack under conditions sufficient to consolidate saidstack into a substantially planar, unitary multi-layer article.
 24. Theprocess of claim 21 wherein the polymeric tapes comprise at least 95% byweight of ultra-high molecular weight polyethylene filaments and whereinsaid layer formed from the polymeric tapes comprises at least 95% byweight of ultra-high molecular weight polyethylene filaments.
 25. Theprocess of claim 21 wherein each of said yarns comprise a plurality ofcontinuous polymeric filaments that are twisted together and bondedtogether.
 26. The process of claim 25 wherein said yarns comprise aplurality of continuous polymeric filaments that are twisted togetherand bonded together with at least about 3 twists per inch of yarn lengthand less than about 15 twists per inch of yarn length.
 27. The processof claim 26 wherein said tapes have an average cross-sectional aspectratio of at least about 10:1.
 28. A process for forming a multi-layerarticle comprising performing steps a)-d) of claim 27 at least twice tothereby form a plurality of layers, arranging said plurality of layersinto a stack, and thereafter applying heat and/or pressure to said stackunder conditions sufficient to consolidate said stack into asubstantially planar, unitary multi-layer article.
 29. The process ofclaim 27 wherein the polymeric tapes comprise at least 95% by weight ofultra-high molecular weight polyethylene filaments and wherein saidlayer formed from the polymeric tapes comprises at least 95% by weightof ultra-high molecular weight polyethylene filaments.
 30. The processof claim 21 wherein said tapes have an average cross-sectional aspectratio of at least about 10:1.
 31. The process of claim 21 wherein eachof said polymeric tapes has an ultimate tensile strength of at least 15g/denier.
 32. The process of claim 21 wherein each of said polymerictapes has an ultimate elongation of at least 5.0%.
 33. The process ofclaim 21 wherein each of said polymeric tapes has an ultimate tensilestrength (g/denier) and each of said polymeric tapes has an ultimateelongation (%), wherein the value of the ultimate tensile strength ofeach tape multiplied by the ultimate elongation of the tape is at least150.
 34. The process of claim 33 wherein each tape comprisespolyethylene filaments.
 35. The process of claim 21 wherein the ultimateelongation (%) of said tape is greater than the ultimate elongation (%)of said multi-filament yarn.